Many different types of pointing devices have been developed for inputting commands into a machine. For example, hand-manipulated pointing devices, such as computer mice, joysticks, trackballs, touchpads, and keyboards, commonly are used to input instructions into a computer by manipulating the pointing device. Such pointing devices allow a user to control movement of a cursor (i.e., a virtual pointer) across a computer screen, select or move an icon or other virtual object displayed on the computer screen, and open and close menu items corresponding to different input commands.
Pointing devices have been developed for large electronic devices, such as desktop computers, which are intended to remain stationary, and for small portable electronic devices, such as cellular telephones and mobile computer systems. Pointing devices for large electronic devices typically have fewer and more flexible design constraints than pointing devices for portable electronic devices because of the greater space and power resources that are available. In general, a pointing device for use in portable electronic devices should allow a user to move a cursor quickly and accurately, operate in an intuitive fashion, and operate within limited workspace and power constraints.
Displacement type pointing devices have been developed to meet the constraints inherent in portable electronic devices. These types of pointing devices include a displaceable member (e.g., a puck, button, or other movable body) that moves in a defined field of motion upon application of force by, for example, a user's finger. When the user releases the displaceable member, a restoring mechanism (e.g., a set of springs) typically returns the displaceable member to a central location within the field of motion. A position sensor determines the displacement of the displaceable member within the field of motion and typically maps the displacement of the displaceable member to the velocity of the cursor. The position mapping system typically fixes the position of the cursor on the display after the restoring mechanism has returned the displaceable member to the central location of the field of motion.
In a typical displacement-type pointing device, the displaceable member moves in two dimensions in response to lateral forces that are directed in an x-y plane. The two-dimensional movements of the displaceable member are mapped to two-dimensional motion of a cursor on a display. In addition to being responsive to lateral forces, it oftentimes is desirable for the displacement-type pointing device to include functionality for detecting vertical or z-axis forces that are applied to the displaceable member along a z-axis that is normal to the x-y plane. The detection of such z-axis forces could be used, for example, to produce signals for controlling the selection of objects that are presented on the display or controlling the width of a virtual line being drawn on the display.
What are needed are displacement type pointing devices and methods that that can detect with high accuracy user inputs that are applied to the displaceable member in vertical as well as lateral directions.